Pyramidal neurons in thick (500 fm) slices of the rat hippocampus were impaled with a microelectrode, electrically characterized and injected with lucifer yellow. The dye was imaged in 3-D using a confocal light microscope. The electrical characteristics of the neurons, particularly firing rate and bursting behaviors, were correlated with their 3-D morphology. The images were traced by our automated tracing software and in the BMIRR's Sterecon system. The apical dendrites were traced and quantitated with respect to their length, branching pattern, and 3-D distribution. It has been stated by other workers, using less accurate means, that certain dendritic patterns correspond to specific electrical characteristics in these neurons. Our work is investigating this hypothesis in young animals and due to the confocal imaging and Sterecon analysis will be able to analyze this question more thoroughly than has been previously possible. Initial results indicate that the conclusions of the previous workers does not apply to developing animals. If this result is further substantiated, it will have important implications for understanding hippocampal development and possibly childhood seizures. Parts of this work were published in 1995 in the Journal of Neurophysiology.